UPDATE: Trump supporters are complaining that their e-mails are being redirected to SPAM filters by Google and Apple (likely Gmail users on Apple devices). There’s a long Reddit thread filled with conspiracy theories and multiple tweets:
One screenshot tweeted by a user lends insight into Google’s reason for doing so:
“We’ve found that lots of messages from donaldjtrump.com are spam.”
It also looks like AdAge weighed in on this issue back on June 13th:
By typical email marketing standards, Donald Trump's spam complaint rate is tremendous -- tremendously high.
Recipients marked nearly 8% of the emails sent by the presumptive Republican presidential nominee's campaign as spam, according to email measurement firm Return Path. By comparison, none of likely Democratic nominee Hillary Clinton's emails were deemed spam.
(emphasis below is mine)
The Trump campaign's spam rate "is extremely, extremely high," said Tom Sather, senior director of research at Return Path. The high spam complaint rate could indicate that many of the email addresses in the Trump campaign's list were purchased rather than gathered through organic voter sign-ups. If people received the emails without actually signing up for them, they may have rejected them.